Apparatus for executing activities assisted by hydromotors and a hydraulic transformer for use in such an apparatus

ABSTRACT

The invention relates to an apparatus for executing activities assisted by equipment driven by means of rotating or linear hydromotors. The hydromotors may be loaded and/or moved in two directions. The hydromotors are coupled via a connecting line and a hydraulic transformer with a high-pressure line. The hydraulic transformer is provided with adjusting means for controlling the hydromotor and control means are provided for restricting the fluid flow in the hydraulic transformer.

CROSS-REFERENCE TO PRIOR APPLICATION

This is a U.S. National Phase application under 35 U.S.C. § 371 ofInternational Patent Application No. PCT/NL99/00067, filed Feb. 10,1999, and claims the benefit of Netherlands Patent Application No.1008256, filed Feb. 10, 1998 and European Patent Application No.98200454.1, filed Feb. 13, 1998, all of which are incorporated byreference herein. The International Application was published in Englishon Aug. 12, 1999 as WO 1999/40318 under PCT Article 21(2).

FIELD OF THE INVENTION

The invention relates to an apparatus for executing activities assistedby equipment driven by means of rotating or linear hydromotors, whichmay be loaded or moved in two directions. A disadvantage of the knownapparatus is that with load variations on the hydromotor, the speed ofthe hydromotor varies also. Load reduction may create dangeroussituations due to the sudden great increase in speed. Anotherdisadvantage is that all the energy present in the high-pressure linemay be used by this particular hydromotor. This means that no moreenergy would come available for the other hydromotors, which would be adisadvantage. It is the object of the invention to avoid the abovedisadvantages. It is possible to achieve hereby that with the aid of thecontrol means the speed and/or energy consumption of the hydromotor isrestricted, so that the above-mentioned disadvantages do not occur.

SUMMARY OF THE INVENTION

The present invention is directed towards an apparatus for executingactivities assisted by equipment driven by means of rotating or linearhydromotors, wherein the apparatus includes control means forrestricting a fluid flow in a hydraulic transformer. In accordance withone aspect of the invention, the control means comprise at least onesensor. Direct or indirect measurement of the flow rate through thehydraulic transformer former with the aid of a sensor, is a simplemanner for obtaining a signal that can be used by the adjustment means.

In accordance with a further improvement, the sensor forms a part of aflow restriction value in the high-pressure line to the hydraulictransformer and/or in the connecting line. In this embodiment simplemeans are used for limiting the fluid flow through the hydraulictransformer.

In accordance with another version, the sensor is coupled with adjustingmeans for, subject to the flow rate measured, adjusting the pressure inthe connecting line. In this embodiment the fluid flow in the hydraulictransformer is limited, while simultaneously preventing loss of energyresulting from throttling the fluid flows.

In accordance with a further improvement, the pressure source comprisesan aggregate wherein the control means are adjusted such that thehydromotor uses less power than an adjustable valve which is, forexample, a portion of the power aggregate is capable of supplying. Thisembodiment achieves that there is always sufficient energy for all userscoupled to the high-pressure line, so that these are able to continue tooperate.

In accordance with a further improvement, the hydraulic transformer isprovided with means to cause the pressure in the connecting line tooscillate around an adjusted valve. This embodiment achieves in a simplemanner that low speeds can be realized with the hydromotors, even athigh loads.

In accordance with a further improvement, the hydraulic transformer hasa continuously variable setting controlled by the adjustment means. Thisembodiment achieves that the system can also be used for the recovery ofenergy in rapidly changing conditions, such as during deceleration ofmoving mass when a movable drive is used, and wherein the vehicle can bemanipulated in the usual manner by the operator of the vehicle. Therapid change of the pressure ratio is an improvement also for thedynamic control and arrest of mass coupled with a motor.

In accordance with a further improvement, the adjusting means areprovided with spring-activated elements for returning the hydraulictransformer into a neutral position wherein the pressure in theconnecting line is minimal. This embodiment achieves that the hydromotoris not loaded if the control breaks down.

In accordance with a further improvement, the hydromotor is a linearcylinder connected with the hydraulic transformer by means of oneconnecting line which is provided with means for at tinder pressuresupplying fluid from the low pressure line. If the setting of thehydraulic transformer is such that quick retraction occurs in the linearcylinder, it is possible by this embodiment to prevent the occurrence ofan underpressure in the cylinder, which could cause cavitation.

In accordance with a further improvement, the apparatus is embodiedaccording to claim 10. This embodiment provides the possibility thatsome of the motors can give a higher torque due to their being driven ata higher pressure than the system pressure prevailing in thehigh-pressure line. This allows the high-pressure line to be designedfor a lower pressure, which is more economical.

The invention also comprises a hydraulic transformer for use in anapparatus, wherein a first fluid flow having a first pressure istransformed into a second fluid flow having a second pressure. Such ahydraulic transformer is disclosed in WO 9731185. The known apparatushas the disadvantage that if a fluid chamber is sealed by the face platewhile there is considerable variation in the chamber's volume due torotation of the rotor and there is no change in the amount of fluid thatis present, the pressure in the fluid chamber may drop too low, whichmay cause cavitation. This drop in pressure may be reduced by making theangular deflection at which the fluid chamber is completely sealed, assmall as possible. However, this has the disadvantage that there is moreleakage along the face plate between the various line connections, whichlowers the performance of the apparatus. It is the object of theinvention to eliminate the afore-mentioned disadvantage and to this endthe volume of the fluid chambers to be sealed by means of the face platehas a maximum value which is less than four times the minimum value ofthe volume to be sealed. By making use of the oil's elasticity and byensuring that a relatively large minimum volume remains, cavitation isprevented, so that the mechanical life of the transformer is notshortened and there is hardly any noise nuisance.

In accordance with a further improvement of the hydraulic transformer,the volume of the fluid chambers to be sealed by means of the face plateis maximally three times as large as the minimum. By this embodimentcavitation is further prevented.

In accordance with a further improvement, the the rotor has nine ortwelve fluid chambers. By this embodiment, fluctuations of the torquecaused by the oil pressure in the fluid chambers and brought to bearupon the rotor are kept at a minimum, as a result of which the axialforce the rotor brings to bear upon the face plate, is also kept at aminimum. This facilitates adjustment of the hydraulic transformer.

In accordance with a further improvement, the face place gates and therotor gates are dimensioned such that at least two rotor gates are ofthe same size and all three walls between the rotor gates simultaneouslyseal off a free plate gate. This embodiment further limits thefluctuations of the torque brought to bear upon the rotor.

In accordance with another version of the hydraulic transformer, thetransformer transforms a first fluid flow having a first pressure into asecond fluid flow having a second pressure. Such an apparatus isdisclosed in WO 9731185. The known apparatus is limited in itsapplications because it is not possible over a large working area tocompletely transform the pressure ratios of two of the line connections.It is the object of the apparatus according to the invention toeliminate this disadvantage, and to this end is embodied according tothe characterizing part of claim 15. By this embodiment, the pressureratio between the line connections over a large working area cancompletely be reversed through the rotation of the face plate, whichbroadens the applicability of the apparatus.

In accordance with a further improvement of the apparatus, the faceplate at the side of the fluid chambers is bordered by a firstseparating surface and at the side facing away from the second chambersby a second separating surface. The first separating surface comprisesat least three rotor gates located at a first radius and being incommunication with three face plate conduits, wherein the third faceplate conduit is in communication with a housing gate located at a thirdradius which is different from the second radius. This embodiment is asimple manner of providing conduits whose orifices are sufficientlylarge, so that little loss of current occurs at the various convenientrotation positions of the face plate.

In accordance with one version, the third face plate conduit is incommunication with a housing gate at the circumference of the faceplate. This embodiment achieves that pressure fluctuations in the thirdface plate conduit do not influence the axial forces around the faceplate, making it simple to bring the same into equilibrium.

In accordance with one version, the third face plate conduit is incommunication with a housing gate near the rotation axis of the faceplate. This embodiment makes it possible for the face plate to becompact.

In accordance with a further improvement, at the second separatingsurface, the housing is provided among other things with four face plategates. By this embodiment the two housing gates located at the firstradius are in all the face plate's positions in communication with largeconduits in the housing, with the result that the flow resistance isminimal.

In accordance with a further improvement the hydraulic transformer isembodied according to claim 20. By this embodiment the shuttle valve isoperated quite simply when the face plate is readjusted.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be elucidated with reference to an illustration of anembodiment, wherein

FIG. 1 shows a cross section of a hydraulic transformer based on anaxial piston pump,

FIG. 2 shows a view according to II—II of the face plate of thehydraulic transformer of FIG. 1,

FIG. 3 shows a cross section according to III—III of the face plate ofthe hydraulic transformer of FIG. 2,

FIG. 4 shows the face plate of FIG. 2 as seen from the opposite side,

FIG. 5 shows a view according to II—II of FIG. 1 of the housing of thehydraulic transformer without face plate,

FIG. 6 schematically shows the coupling between the face plate conduits,the gates in the housing and a motor coupled with the pressuretransformer,

FIG. 7 shows a schematic view as in FIG. 6, with the face plate being ina different position in relation to the housing, and the motorencountering a reversed load,

FIG. 8 shows a schematic view of the different positions of the faceplate in the various deployment conditions and load situations of themotor coupled with the hydraulic transformer,

FIG. 9 shows a schematic view of a second embodiment of a hydraulictransformer, coupled with a double-acting hydraulic cylinder,

FIG. 10 schematically shows a third embodiment of a hydraulictransformer with a single-acting hydraulic cylinder,

FIG. 11 shows a diagram of the working range of a hydraulic transformer,

FIG. 12 schematically shows an embodiment of a hydraulic transformerwith a control system, and a hydromotor, and

FIG. 13 shows a simplified version of the embodiment of FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Similar parts in the various figures are identified as much as possibleby identical reference numbers.

FIG. 1 shows a hydraulic transformer. It shows a bent housing 3 inaccordance with the bent housing of an axial piston pump, from whichsaid hydraulic transformer is more or less derived. At one side in thebent housing 3, a swivel axle is rotatably mounted by means of twoswivel axle bearings 15. The swivel axle 1 is able to freely rotatearound a rotation axis 16. The bent housing 3 comprises also a rotatablerotor 2, mounted on an axis 13. The rotor 2 rotates around the axis 13which is mounted on the swivel axle 1. A rotation axis 11 of the rotor 2forms an angle with the rotation axis 16 of the swivel axle 1, wherebysaid rotation axes 11 and 16 intersect.

The swivel axle 1 is also provided with pistons 14, which can move inthe longitudinal direction in the cylindrical chambers 12 of the rotor2. The pistons 14 couple the rotation of the swivel axle 1 with therotation of the rotor 2. The joint rotation of the rotor 2 and theswivel axle 1, and the fact that the rotation axis 11 of the rotor 2 andthe rotation axis 16 of the swivel axle 1 form an angle, cause thepistons 14 in the cylindrical chambers 12 to move to and fro, therebycausing the volume of the cylindrical chambers 12 to vary between aminimum and a maximum. Via a rotor conduit a, each of the cylindricalchambers 12 is in communication with face plate gates 30 located in asealing surface V1.

The rotor 2 is sealingly fastened to a face plate 10 by means of thesealing surface V1, and the face plate 10 is sealingly fastened to ahousing 5 by means of a sealing surface V2. The housing 5 and the benthousing 3 are attached to one another by means of bolts, which are notshown. The face plate 10 is rotatably mounted in the housing 5 by meansof face plate bearings 9, whereby it is able to rotate around a rotationaxis 11 which coincides with the rotation axis 11 of the rotor 2. Thebearings 9 are designed such that the face plate 10 is able to move inthe direction of the rotation axis 11, that in the cylindrical chambers12 the rotor 2, under the influence of the oil pressure pushes, amongother things, against the face plate 10, and the face plate against thehousing 5. Any oil leakage along the surfaces V1 and V2 is therebyavoided as much as possible.

By means of an adjusting shaft 8, the face plate 10 can be rotated andthus adjusted. The rotation of the face plate 10 is limited toapproximately 180° by means of a pin 4. In the housing 5 radial housingbores 6 are provided and a central housing bore 7.

The bearings 9 of the face plate 9 are necessary to prevent the faceplate from tilting under the influence of the asymmetrical pressures inthe sealing surfaces V1 and V2. These asymmetrical pressures develop dueto the varying oil pressures in the various orifices in the face plate10 and they depend, among other things, on the rotation position of theface plate 10. Should the face plate 10 be able to tilt, inadmissibleleakages could develop along the surfaces V1 and V2. The bearings 9 aretherefore designed such that the face plate 10 is able to move in theaxial direction but cannot tilt. In order to further minimize theleakage in the surfaces V1 and V2 ensuing from tilting of the face plate10 which could occur due to play in the bearings 9, the surfaces V1 andV2 are spherical with the centre of the sphere being located on therotation axis and the surface of the sphere being directed outward. Thisdiminishes the extent to which tilting affects leakage.

The rotor 2 can rotate around the rotation axis 11, thereby varying thevolume of the cylindrical chambers 12. Via the face plate gates 30 andthe conduits b in the face plate 10, the cylindrical chambers 12 are incommunication with one or two of the radial housing bores 6 of thecentral housing bore 7. The face plate 10 is kept in the housing 5 at amore or less constant rotation position, unless said face plate is beingadjusted by means of the adjusting shaft 8. Due to the effect of thedifferent pressures prevailing in the central housing bore 7 and theradial housing bores 6, the pressure in the various cylindrical chambers12 varies, with the result that at the various chambers different forcesare brought to bear upon the rotor 2, causing the rotor 2 to rotate.This induces the flow of oil through the housing bores 6 and 7, thepressure ratio in the various housing bores depending, among otherthings, on the position of the face plate 10. The sealing surfaces V1and V2 are, in accordance with the known art, finished with care, sothat there is hardly any leakage between the rotor 2 and the face plate10 or between the face plate 10 and the housing 5 respectively. Thecylindrical chambers 12 have a varying volume which during rotation ofthe rotor 2 is periodically sealed by the face plate 10 at the faceplate gate 30. While being sealed, the volume in the cylindricalchambers 12 still varies, causing the pressure to rise or drop due tothe rotation of the rotor 2. If the cylindrical chamber 12, sealed bysurface V1, has a dead volume of at least 25 to 50% of the stroke volumeof the piston 14, there is no cavitation which shows that the pressuredrop is staying within acceptable limits. This means that the maximumvolume sealable by the face plate is smaller than three to five timesthe minimum of the sealable volume. Due to the fact that the expandingoil prevents the pressure in the cylindrical chamber 12 from droppingtoo low, cavitation is prevented. This in turn reduces wear and thenoise level.

As a result of the cylindrical chambers 12 being sealed and of therebeing a limited number of cylindrical chambers, for example, in thiscase 7 chambers, the rotation of the rotor 2 caused by the pressurevariations in the cylindrical chambers 12 and the ensuing fluctuation ofthe torque on the rotor 2, is not completely regular and are therotation of the rotor 2 and the swivel axle 1 subject to decelerationand acceleration. This will cause the hydraulic transformer to exert avarying torque on its bedplate which, through resonance, may cause noisenuisance. Noise nuisance can be prevented by placing the hydraulictransformer on rubber blocks, thereby allowing it to make smallmovements and by making the lines flexible.

FIG. 2 shows the face plate 10 in the sealing surface V1 with ahigh-pressure rotor gate 17, a first rotor gate 18 and a second rotorgate 18′. These gates collaborate with the face plate gates 30. Betweenthe rotor gates 17, 18 and 18′ wide walls 23 are provided, the width ofthe wide wall 23 being such that a cylindrical chamber 12 via the faceplate gate 30 is always only in contact with one of the rotor gates 17,18 or 18′. As discussed above, it has been shown that when the rotor 2rotates, the torque exerted by the swivel axle fluctuates as a result ofthe different fluid pressures in the cylindrical chambers 12. If thereare three rotor gates 17, 18 and 18′, this undesirable fluctuation canbe limited by having as many cylindrical chambers 12 as possible. Byproviding cylindrical chambers 12 in multiples of three, the axial forceexerted by the rotor 2 on the face plate 10 is minimal, resulting in areduction of wear. Preferably there are nine or twelve cylindricalchambers because this is the number with which to achieve theabove-mentioned advantages in the most optimal manner.

Over a curve of, for example, approximately 180° the circumference ofthe face plate 10 is provided with toothing 22 and the other 180° areprovided with a groove 19 interacting with the earlier-mentioned pin 4.The adjusting shaft 8 engages the toothing 22. The lengths of the rotorgates 17, 18 and 18′ may be identical but, depending on the application,may also be different. Due to the groove 19 and the toothing 22 providedover half of the circumference, the rotation of the face plate 10 in thehousing 5 is restricted to about 180°, the high-pressure rotor gate 17being able to rotate over 90° to both sides in relation to the positionin which the volume of the cylindrical chamber 12 is the smallest (thisposition is called the Top Dead Centre TDC). By shortening the groove 19or by using two pins 4, the maximum rotation angle can be reduced toless than 90° either side. This limits the maximally attainable pressureratios, so that, for example, the pressure in the first or second rotorgate is restricted to twice the pressure in the high-pressure rotorgate, or whereby the maximum pressure in the one load direction can bemade different to that in the other direction.

In accordance with an embodiment of the face plate 10, the rotor gates17, 18 and 18′ and the walls 23 are dimensioned such that the axialforces from the rotor 2 on the face plate 10 are at all rotationpositions as low as possible. The rotor gates 18 and 18′ are identicalin size and symmetrical in relation to one another, and the centres ofthe walls 23 form an angle with one another which is a multiple of thepitch angle between the rotor gates 30, distributed evenly over thecircumference. The width of a wall 23 in the direction of rotation isapproximately, with a tolerance of one degree, the same as the width ofa face plate gate 30 in the direction of rotation. In this embodimentthe rotor 2 may also assume a rotation position in which the walls 23are covered by the portion of the rotor 2 that is located between theface plate gates 30. The oil leakage between the rotor gates 17, 18 and18′ is then minimal. In the situation where the face plate 10 isadjusted such that, subject to the load from the users connected to thehydraulic transformer there is no oil flow, the pressures in thecylindrical chambers 12 and the forces on the rotor 2 will cause thesame to come to a stand-still, because this is the most stable position.

The face plate 10 is rotated by means of the axle 8. In order to realizean engagement without play between the toothed wheel on the axle 8 andthe toothing 22, several known measures can be taken, such as renderingthe centre-to-centre distance between the axle 8 and the rotation axisof the face plate 10 adjustable. To this end the bush in which an axle 8rotates is designed in the known manner as eccentric bush. The axle 8may be driven by means of a manually operated lever. As will be shownbelow, the axle 8 may also be driven by means of a servo-motorcomprising a control system. Alternatively, the manual operation may belimited by blockages which are adjustable by means of a control system.

FIG. 3 shows a cross section of the face plate 10. It can be seen howvia a conduit b, the high-pressure rotor gate 17 is in communicationwith the centrally positioned high-pressure housing gate 21. Via aconduit b the first rotor gate 18 is in communication with a firsthousing gate 20, located at a radius at the side of the gate plate 10facing the housing 5.

FIG. 4 shows the view of the surface V2 of the face plate 10. Theposition of the first housing gate 20, a second housing gate 20′ and thehigh-pressure housing gate 21 are visible. the length of the firsthousing gate 20 and the second housing gate 20′ is slightly less than90°.

In FIG. 5 the housing 5 is shown, illustrating the connections of theradial housing bores 6 and the central housing bores 7, which terminatein the sealing surface V2 with a face plate gate 24. In the centre ofsurface V2 a central housing bore 7 is provided, and surrounding it arethe four evenly distributed face plate gates 24. Between the face plategates 24 there is a narrow wall 25. The central housing bore 7 adjoinsthe high-pressure housing gate 21, and the face plate gates 24 adjointhe first housing gate 20 and second housing gate 20′. The dimensions ofthe first housing gate 20 and the second housing gate 20′ are such thatthey cover approximately one face plate gate 24. It is essential that inthe various positions of the face plate 10, always two face plate gates24 work together such as to allow the oil to flow from the first housinggate 20 or the second housing port 20′ with little loss of current.

FIGS. 6 and 7 schematically show the connections of a hydraulictransformer HT, the manner in which they are provided with energy via afeed pressure P, and the oil discharge having a tank pressure T, and howa rotating motor 27 is connected in the case of a varying load device.FIG. 6 schematically shows the face plate 10, positioned at a adjustingangle δ. The face plate gates 24 are represented schematically as thecurved lines 24 a, 24 b, 24 c and 24 d and correspond to the face plategates 24 shown in FIG. 5. The first housing gate 20 works together withtwo face plate gates 24 a and 24 b. Due to the adjusting angle δ, thefirst housing gate 20 has a working pressure B, the second housing gate20′ has the tank pressure T, if the high-pressure cylinder gate has afeed pressure P. Said pressures bear a certain relation to one anotherwhich, among other things, depends on the adjusting angle δ. For theworking pressure B to be able to take on a value that may exceed that ofthe feed pressure P by approximately 50%, it is necessary that theadjusting angle δ can be adjusted to a maximum of 90°. The first housinggate 20 is then in open communication with the two face plate gates 24 aand 24 b. Via a shuttle valve 26, said conduit gates 24 a and 24 b arein communication with one another and are coupled to a first connection29 of the rotating motor 27. In a similar manner the face plate gates 24c and 24 d connected with the second housing gate 20′, are connectedwith a second connection 28 of the rotating motor 27. When comparingFIGS. 6 and 7, wherein the adjusting angle δ in FIG. 7 has acquired anopposite value with the result that the pressures on the rotating motor27 have also acquired an opposite value, the necessity for the firsthousing gate 20 to also be in communication with the face plate gate 24c becomes obvious, and for that purpose the shuttle valve is turned.

The adjustment of the shuttle valve 26 depends entirely on the positionof the face plate 10 and may thus be coupled thereto. This may be amechanical coupling; the face plate 10 may, for example, be a cam discwhich operates the shuttle valve 26. It may also be anelectro-mechanical mechanical or electrohydraulic coupling. The faceplate 10 may also be provided with gates (not shown) which work togetherwith orifices in the housing so that they have the effect of valve 26.Instead of coupling the shuttle valve 26 with the face plate 10, it isalso possible to adjust the shuttle valve 26 in relation to the pressureat the motor connections 28 and 29, since they also depend on theadjusting angle δ.

Apart from the above embodiment having a central housing bore 7 workingtogether with the high-pressure housing gate 21, there are also otherpossible embodiments. For example, a first alternative embodiment isthat instead of the central housing bore 7 in surface V2, a annularconduit is provided in housing 5 or in the face plate 10, workingtogether with a bore in the face plate 10 or the housing 5 respectively.Said annular conduit is then provided at a different radius to that ofthe face plate gates 24. A second alternative embodiment is, forexample, that the above-mentioned annular conduit is provided at thecircumference of the face plate 10, either in the face plate 10 or inthe housing 5. Said annular conduit then also works together with a boreprovided in the housing 5 or in the face plate 10, respectively. Thisembodiment has the advantage that if the pressure in the annular conduitvaries, the forces exerted in the direction of the rotation axis 11 onthe face plate 10, do not vary; as a result of which the forces on theface plate 10 ensuing from the pressures in the various gates can beequilibrated more easily in the different work situations. Instead ofthe above-mentioned embodiment comprising an annular conduit and a bore,with the annular conduit extending over the maximal rotation angle ofthe face plate 10, it is also possible to provide two annular conduits,one in the housing and one in the face plate 10, the length of theannular conduits being such as to allow the face plate 10 to make thedesired rotation.

In the embodiment shown, the face plate 10 is bearing-mounted inbearings 9. The face plate may also be provided with different bearings,always ensuring that rotation and axial displacement are possible andthat tilting is prevented. For example, it is possible to use static oilpressure bearings, or to provide an axle or tube at the rotation axis 11projecting into the housing 5 and being bearing-mounted in the housing,and which can simultaneously be employed for the rotation of the faceplate 10. The tubular axle may then be in coupled with the centralhousing bore 7.

The above-described construction comprising a shuttle valve 26 is inparticular necessary if the face plate 10 is required to rotate over awide angle, as is the case in the embodiment shown. If the rotationangle is permitted to be smaller, for example, because chambers are usedwhose volume acquires a minimum and a maximum value twice or more oftenper rotator rotation, and if the embodiment of the face plate isadapted, the rotation the face plate is required to make to operate issmaller, and it is not necessary to use a shuttle valve to ensure thatthe flow orifices are large enough. However, there may be occasions whentheir use will nevertheless give better results.

In the interior of the bent housing 3, leak-off oil will flow along theseparation surfaces V1 and V2. Since the bent housing 3 does not have arotating exiting axle with a pressure-sensitive seal—as the swivel axle1 is not driven—the development of an overpressure in the bent housing 3is permissible. As the overpressure may be equal or higher than the tankpressure T, the interior of the housing 3 is, in a manner not shown, incommunication with the face plate gate 24 c and consequently with thetank connection T.

FIG. 8 shows schematically the application of the hydraulic transformerwhen the same is connected to a rotating motor 27, as indicated in theFIGS. 6 and 7. The description is applicable in a similar manner ifinstead of a rotating motor 27 a double-acting hydraulic cylinder aslinear motor is coupled to the hydraulic transformer. Instead ofrotation and torque, displacement and load are then involved.

In the diagram of FIG. 8 the rotation speed of the motor 27 is plottedin four quadrants on the horizontal axis against the loaded torque. In afirst quadrant I the motor moves forward at a positive speed ω, driving,for instance, a device or object at a positive torque T. In the secondquadrant II the motor moves forward at a positive speed ω, the device orobject mass is being decelerated at a negative torque T. In the thirdquadrant III the motor moves in the opposite direction and the speed ωis negative and the device or object is driven in that direction also,such that the torque T is also negative. In the fourth quadrant IV thedirection of movement of the device or object is still opposite so thatthe speed ω is negative, but this negative speed is being decelerateddue to the torque being positive.

The torque T of the motor 27 is limited by the maximally allowablepressure in the system which is formed by the hydraulic transformer, thecoupling lines and the motor; the speed ω is limited by the allowablespeed of the motor, and each quadrant is also limited by the maximumpower to be produced, which is shown by the hyperbolical boundary of thequadrants.

As shown in the diagram, the pressure ratio at the rotor gates 17, 18and 18′ is determined by the rotation position of the face plate 10, inthe diagram indicated by the adjusting angle δ in relation to TDC, whichis the Top Dead Centre, that is the position of the rotor 2 at which thevolume of the cylindrical chamber 12 is maximal. As discussed above, thefirst rotor gate 18 and the second rotor port 18′ are joined with theconnections of the motor 27, and the feed pressure P is joined with thehigh-pressure rotor gate 17.

The rotation of the motor 27 at rotation speed ω occurs through theeffect of the torque T, which torque T depends, among other things, onthe resistance and the acceleration and deceleration of the devices andobjects driven by the motor 27. The rotation of the motor 27 causes theflow of oil and also the rotation of the rotor 2 at a rotation speed r.The direction of the rotation and the speed r of the rotor 2 depend onthe direction of the rotation and the rotation speed ω of the motor 27.

In order to be able to react to varying loads, the face plate has to bequickly adjustable and rotatable. For example, when the hydraulictransformer is used with the motor in a mobile drive, it is essentialthat it is possible to quickly switch from movement to deceleration, andto this end it is necessary that within 500 msec the load of the motor27 can be completely reversed by means of a 180° rotation of the faceplate 10. This means that within 500 msec the face plate 10 can beturned 180° from the first extreme operative position to the secondextreme operative position, transforming the maximal working pressurefrom the first motor connection 28 to the second motor connection 29 andvice versa.

In order for the system to respond properly to load fluctuations due to,for example, varying loads, a feed-back control system is used for thedrive of the face plate, wherein feedback may be effectuated throughmeasuring the speed of the motor (speed feedback) or through measuringthe load of the motor (load feedback).

Speed feedback may ensue when the rotation speed r of the rotor ismeasured or when the pressure drop at throttling resulting from an oilflow, is measured. Load feedback may ensue when the pressure differencebetween the first housing gate 20 and the second housing gate 20′ ismeasured. The drive of the face plate 10 and the applied control systemare attuned such that a response frequency of minimally 3.5 Hz, andpreferably a response frequency of minimally 7 Hz is realized. Thismeans that the face plate 10 has to be able to rotate quickly from theintermediate position to the maximum position, in other words 900, forinstance within 100 to 200 msec. To this purpose the drive of the faceplate 10 may comprise an electric servomotor coupled to the adjustingaxle 8. Alternatively, the face plate 10 can be adjusted by means of ahydraulic cylinder comprising a rack which engages (not shown) thetoothing 22 of the face plate 10, and which is adjustable by means of aservo valve.

FIG. 9 shows a double-acting hydraulic cylinder 32 comprising a housing31 with a vertically movable piston 33. The piston is movable in bothdirections x and in doing so, is able to exert a force P in bothdirections. Thus the double-acting hydraulic cylinder 32 can be used ina similar manner as in the application of the rotatable hydromotordescribed in FIG. 8, and is therefore suitable for four-quadrant use. Atthe bottom side, the housing 31 and the piston 33 form a chamber 34which via a connecting line 38 is in communication with a connection ofa hydraulic transformer 40. Via a connecting line 37, a chamber 35formed by the top of the piston 33 and the housing 31, is incommunication with the hydraulic transformer 40. The hydraulictransformer 40 is a simple embodiment of the hydraulic transformerdescribed in the preceding figures. The simplification consists in thefact that the line connections such as the high-pressure line P and theconnecting line 37 and 38 are in communication with the three conduitsin the face plate. To ensure that in certain load situations the masscontinues to be appropriately equilibrated in the hydraulic transformer40, it is necessary to transport fluid from or to the tank connection T.To ensure that said transport to the pressure-less line of the hydraulictransformer 40 takes place, a valve 36 is provided which operates viathe position of the face plate or the pressure in the connecting lines37 and/or 38. The leak-off oil in the hydraulic transformer 40 isdischarged to the tank connection T via a leak-off oil drainage 39.

FIG. 10 shows a single-acting hydraulic cylinder 41 comprising a housing31 and a piston 33. The piston 33 is movable in both directions x and isable to exert a force in one direction P. Thus the single-actinghydraulic cylinder 41 is only suitable for use in a first and fourthquadrant as shown in FIG. 8, where instead of torque and rotation onehas to read load and displacement. A connection line 38 couples thesingle-acting hydraulic cylinder 41 to a hydraulic transformer 41, whichis comparable to the above-mentioned hydraulic transformer 40, and inwhich the rotation of the face plate is limited so that the pressure inthe connecting line 37 never exceeds the pressure in the tank connectionT. Due to inertia of the piston 33 or the mass connected with it, it ispossible that when the face plate is being adjusted, the connecting line38 becomes pressure-less to the extent that said pressure line 38 or thechamber 34 become cavitated. In order to avoid this, the connecting line38 is in communication via a non-return valve 43 with the tankconnection T.

The diagram of FIG. 11 shows the working range of a hydraulictransformer, wherein the same is fed from a high-pressure line having aconstant pressure P, and is coupled to a motor, for example, a rotatinghydromotor. The constant working pressure P is generated by means of anaggregate. In the diagram the pressure P is plotted against the volumeoil flow Q to the hydromotor. To protect the hydraulic transformer, theconnecting lines and the motor against overloading, the pressure islimited to P_(max) by restricting the rotation of the face plate. Asalready known, P_(max) may be higher than the pressure in thehigh-pressure line P, so that in a limited number of places in aninstallation, it is possible to use motors with a higher allowablepressure. The values for pressure P and volume flow Q shown in thediagram correspond to the load from the hydromotor and the rotationspeed of the hydromotor respectively. The power produced by thehydraulic transformer and thus also by the hydromotor is indicated bythe dash-dot-lines P₁, P₂ and P₃.

The motor coupled with the hydraulic transformer is controlled byvarying the pressure, which causes the motor to rotate and the volume toflow through the hydraulic transformer. In a high-pressure line having aconstant pressure P, the volume flow may increase without limitation aslong as the load produced by the motor is greater than the load used bythe machine that is being driven. The motor could develop aninadmissible speed, or inadmissibly much power could be used from thehigh-pressure line. The place in the diagram indicated by W is the usedpower P1 and the fluid flow Q₂. The working range is then A+B+C+D, andit is the objective to limit this. By limiting the fluid flow Q to Q₁,the maximum power produced becomes P2 and the working range becomes A+B.This may result in the hydromotor using too much power, so that theaggregate cannot supply enough oil. By limiting the power to be producedby the hydraulic transformer to P₃, the working range is reduced to A+C;it should be borne in mind, however, that there is no restriction to Q₂,so that during load reduction the revolutions of the hydromotor maystill be inadmissibly high. By combining the limitation of the fluidflow and the power, the working range is reduced to A.

FIG. 12 shows how the working range can be limited by means of a controlsystem. A schematically indicated hydraulic transformer 44 comprises anadjustment mechanism for the face plate, which adjustment mechanism 45is operated by an actuator 46. The actuator 46 is controlled by acontrol system 47 which is designed to make the motor move in aparticular manner. In the high-pressure line from a pressure source P tothe hydraulic transformer 44, a sensor 50 is provided which is able tomeasure the flow rate, or which at least emits a signal if the flow rateexceeds a set value. The hydraulic transformer 44 is connected with ahydromotor 48 by means of connecting lines 51. The connecting lines 51are provided with a sensor 49, which is similar to sensor 50. Thesensors 49 and 50 are coupled with the control system 47.

By measuring the oil flow to the hydraulic transformer 44 by means ofthe sensor 50, the power used is measured and the face plate can beadjusted by means of the actuator 46 such that the power used by thehydraulic transformer can be limited to a set value. By measuring theoil flow in the connecting line 51 by means of the sensor 49, the fluidflow can be limited. Instead of measuring the fluid flow directly in theconnecting line 51, it can also be determined in another manner, forexample, by counting the revolutions of the rotor of the hydraulictransformer 44 or of the hydromotor 48.

In addition to the embodiment described above it is also possible forthe control system 47 to comprise an algorithm for calculating thevarious flow rates and/or the power used. For this purpose, the pressurein the high-pressure line is known in the control system 47, forexample, via a sensor or as preset value; for example, via the positionof the actuator 46, the position of the face plate is known and one ofthe rates in the system, such as the flow rate in the high-pressure lineto the hydraulic transformer 44, the flow rate in a connecting line 51,the rotation speed of the hydraulic transformer's rotor or the speed ofmovement of the motor 48, are known.

FIG. 13 shows a simplified embodiment for limiting the fluid flowthrough the hydraulic transformer 44, wherein the adjustment mechanism45 of the face plate is operated manually. In order to limit excessivelyhigh speeds of the motor 48 controlled by the hydraulic transformer 44,a mechanism is provided for restricting the stroke of the adjustmentmechanism 45 if the flow rate in the connecting lines 51 exceed a presetvalue. To the adjustment mechanism 45 a rod 52 is attached, which canslide into a bush. The bush 53 is fastened to a hydraulic cylinder 55,whose piston, when there is insufficient pressure in a signal line 56,is retained in an extreme position by a spring 54. In this position therod 52 can move freely in the bush 53 and the adjustment mechanism 45can be moved freely. In both flow directions in the connecting line 51,a restriction 57 is built in after a non-return valve 58, which above aparticular flow rate in the signal line 56 or a signal line 60, causes abuild-up of pressure. The pressure in the signal line 56 pushes thepiston in opposition to the spring pressure in the hydraulic cylinder 55toward its second extreme position, and pushes the adjusting means 45into a direction such that the flow rate will decrease.

If the flow rate is too high in the opposite direction, the pressurewill increase in the signal line 60, so that an identical cylinder willmove the adjustment mechanism 45 into the opposite direction.

In addition to, or instead of limiting the flow rate as shown here, thepower can be limited in a similar manner.

The above-described embodiment comprising limitation of power to beproduced by a motor, is deployed in situations where several motors andother users are coupled to a common high-pressure line. By means of thecontrol system 47 it is possible to limit the power used by the variousmotors which may, for instance, be necessary if the hydraulic power tobe produced by an aggregate is limited, and if parts of the installationalways have to be available for use.

In addition to the above-described limitation of power and/or speed, inwhich the adjustment is more or less non-dissipative, a simplerembodiment is possible, wherein a flow-limiting valve is provided in thehigh-pressure line to the hydraulic transformer and/or in the connectingline to the hydromotor. Limitation of the flow is realized by throttlingthe oil flow so that energy is lost. Because of the simplicity of theembodiment and the considerable operational reliability, this solutionmay be applied as safeguard in addition to the above-mentioned moreadvanced control system.

An example of the above-described installation is a fork-lift truckcomprising a hydraulic aggregate, where always enough energy must beavailable, for example, for lifting the load. In this deployment thepower used because of the movable drive is, for example, limited to 90%of the aggregate's power, so that always sufficient energy remainsavailable for the lift drive.

The control means 47 discussed above may also be used to control thehydraulic transformer 44 such that displacements at low speed arepossible. The hydraulic transformer controls the movement of thehydromotor 48 by means of fluid pressure with the consequence that, dueto the compressibility of the fluid in the hydraulic transformer and dueto pressure fluctuations during rotation of the hydraulic transformer'srotor, the hydromotor does not immediately start when the adjustmentmechanism 45 is being operated, so that extra provisions are required.Small movements of the hydromotor are possible if during actuation bythe adjustment mechanism the face plate oscillates around the adjustedposition with a deflection of preferably 10 degrees. The oscillationfrequency depends on the hydraulic transformer, the hydromotor 48 andthe connecting lines 51, and may be between 3 and 16 Hz or higher. Inorder to avoid loss of energy during adjustment of the face plate, thefrequency chosen is preferably as low as possible. In practice, 7 Hertzhas been proven to be a good oscillation frequency. The oscillation ofthe face plate around an adjusted position in the afore-described mannerinduces pressure oscillations of the same frequency in the connectingline, and it allows the hydromotor 48 to move at low speed over arelatively large distance, facilitating precise displacements. Anadditional advantage is that the face plate always moves inside thehousing, so that there is always an oil film between the housing and theface plate, with the consequence that less energy is required foradjusting the face plate.

In addition to the above-described manner for oscillating the face plateby means of an actuator 46 controlled by a control system 47, theadjusting mechanism 45 may carry out a hydraulically driven oscillationaround the adjusted value, so that said oscillation can also be applied,for example, in a manually controlled embodiment as described in FIG.13.

Instead of the above-described oscillation of the face plate around theadjusted position it is possible to obtain the same effect if thehydraulic transformer is provided with a mechanism by which the top deadcentre TDC oscillates around a position of equilibrium by means of, forexample, allowing the bent housing 3 (see FIG. 1) to oscillate inrelation to the housing 5. This distinguishes the oscillation from theadjustment of the face plate 10, making it more simple to adjustment theface plate.

1. An apparatus for executing activities assisted by equipment driven bya hydraulic unit, comprising: one of a rotating and a linear hydromotorbeing at least one of loadable and movable in two directions; ahydraulic transformer provided with a rotor and having a continuouslyvariable setting controlled by an adjustment means; a connecting lineconnecting the one of the rotating and linear hydromotor and thehydraulic transformer, the apparatus comprising: a pressure source forstoring and delivering fluid of high pressure, a high-pressure lineconnecting the pressure source and the hydraulic transformer; a tank forreceiving and supplying fluid at low pressure; a low pressure lineconnecting the tank and the hydraulic transformer; and a control meansfor controlling the one of the rotating and linear hydromotor by settingthe adjustment means and thereby setting a fluid pressure in theconnecting line, wherein the control means comprises a means forrestricting a hydromotor load and a hydromotor speed by adjusting theadjustment means based on a feedback of the hydromotor load and thehydromotor speed using a sensor for measuring the flow rate of the fluidflow in the connecting line between the one of the rotating and linearhydromotor and the hydraulic transformer and one of a sensor formeasuring the flow rate of the fluid flow in the high-pressure line tothe hydraulic transformer and an algorithm for calculating thehydromotor load based on the setting of the adjustment means and ameasured flow rate.
 2. An apparatus according to claim 1, wherein thesensor is a flow sensor in the connecting line.
 3. An apparatusaccording to claim 1, wherein the sensor is a revolution sensor formeasuring a rate of rotation of the rotor.
 4. An apparatus according toclaim 1, wherein the sensor is a movement sensor for measuring a rate ofmovement of the one of the rotating and linear hydromotor.
 5. Anapparatus according to claim 1, wherein the sensor comprises a flowrestriction valve disposed in one of the high-pressure line and theconnecting line.
 6. An apparatus according to claim 1, wherein thepressure source comprises: an aggregate having a maximum power rating,and the control means includes a setting so that a power use of the oneof the rotating and linear hydromotor is less than an adjustable valuewhich is a portion of the maximum power rating.
 7. An apparatusaccording to claim 1, wherein the hydraulic transformer is provided withmeans for causing the fluid pressure in the connecting line to oscillatearound an adjustable value at a frequency of at least 3 Hertz.
 8. Anapparatus according to claim 1, wherein the adjustment means comprises acontinuously adjustable setting that is designed to change the settingwithin 500 msec from a first extreme setting via the zero position to asecond extreme setting.
 9. An apparatus according to claim 1, whereinthe adjustment means includes spring-activated elements for returningthe hydraulic transformer into a neutral position wherein the fluidpressure in the connecting line is minimal.
 10. An apparatus accordingto claim 1, wherein the one of the rotating and linear hydromotor is alinear cylinder and the connecting line is coupled to the low-pressureline via a non-return valve.
 11. An apparatus according to claim 1,wherein the hydraulic unit is suitable for a pressure exceeding thepressure prevailing in the high-pressure line.
 12. A hydraulictransformer for use in an apparatus according to claim 1, wherein afirst fluid flow having a first pressure is transformed into a secondfluid flow having a second pressure, comprising a housing, a first lineconnection, a second line connection and a third line connection, arotor which in relation to the housing is limitlessly rotatable, aplurality of fluid chambers whose volume, when the rotor rotates at afirst angle, varies between a minimum and a maximum volume, and a faceplate provided with face plate conduits for, while the rotor isrotating, alternatingly connecting the fluid chambers with the threeline connections, which face plate is rotatable around a rotation axisin relation to the housing and is provided with means for withoutinterruption keeping a face plate conduit in communication with therespective line connection while the face plate is rotating, wherein theface plate, in relation to the housing, is able to rotate at a secondangle wherein the second angle is approximately equal to the firstangle.
 13. A hydraulic transformer according to claim 12, wherein theface plate at the side of the fluid chambers is bordered by a firstseparating surface and at the side facing away from the fluid chambersby a second separating surface, the first separating surface comprisingat least three rotor gates located at a first radius and being incommunication with three face plate conduits, and the second separatingsurface comprising two housing gates located at a second radius, andeach being in communication with a face plate conduit, wherein the thirdface plate conduit is in communication with a housing gate located at athird radius which is different from the second radius.
 14. A hydraulictransformer according to claim 12, wherein the face plate at the side ofthe fluid chambers is bordered by a first separating surface and at theside facing away from the fluid chambers by a second separating surface,the first separating surface comprising at least three rotor gateslocated at a first radius and being in communication with three faceplate conduits, and the second separating surface comprising two housinggates located at a second radius, each being in communication with aface plate conduit and the third face plate conduit being incommunication with a housing gate at the external circumference of theface plate.
 15. A hydraulic transformer according to claim 12, whereinthe face plate at the side of the fluid chambers is bordered by a firstseparating surface and at the side facing away from the fluid chambersby a second separating surface, the first separating surface comprisingat least three rotor gates located at a first radius and being incommunication with three face plate conduits, and the second separatingsurface comprising two housing gates located at a second radius, andeach being in communication with a face plate conduit, the third faceplate conduit being in communication with a housing gate near therotation axis of the face plate.
 16. A hydraulic transformer accordingto claim 12, wherein the face plate at the side of the fluid chambers isbordered by a first separating surface and at the side facing away fromthe fluid chambers by a second separating surface, the first separatingsurface comprising at least three rotor gates located at first radiusand being in communication with three face plate conduits, and thesecond separating surface comprising two housing gates located at asecond radius, and each being in communication with a face plateconduit, at the second separating surface, the housing is provided withfour face plate gates located at the second radius; two face plate gatesbeing positioned diametrically opposite one another and being in directcommunication with the first and the second line connectionrespectively, while the other two face plate gates positioneddiametrically opposite one another are in communication via a shuttlevalve with the first and a second line connection.
 17. A hydraulictransformer according to claim 16 wherein the shuttle valve forms partof the face plate.
 18. A hydraulic transformer according to claim 16wherein the shuttle valve is coupled to the face plate.
 19. A hydraulictransformer according to claim 12, wherein the rotor includes one ofnine and twelve fluid chambers.
 20. A hydraulic transformer according toclaim 12, wherein rotor gates are separated by walls and face plategates and the rotor gates are dimensioned such that at least two rotorgates are of the same size, and the walls between the rotor gates canclose respective fluid chambers, simultaneously, for a particularposition of the rotor.
 21. A hydraulic transformer for use in anapparatus according to claim 1, wherein a first fluid flow having afirst pressure is transformed into a second fluid flow having a secondpressure, the hydraulic transformer comprising a housing, a first lineconnection, a second line connection and a third line connection, arotor which in relation to the housing is limitlessly rotatable having aplurality of fluid chambers whose volume during rotation of the rotorvaries between a minimum volume and a maximum volume, a plurality ofrotor conduits for connecting a plurality of face plate gates with thefluid chambers, and a face plate provided with three rotor gatescooperating with the face plate gates which during rotation of the rotorserve for closing and alternatingly connecting the fluid chambers withthe three line connections, wherein the maximum volume of the fluidchambers to be closed by means of the face plate is maximally five timesas large as the minimum volume.
 22. A hydraulic transformer according toclaim 21, wherein the maximum volume of the fluid chambers to be closedby means of the face plate is maximally three times the minimum volume.23. A hydraulic transformer according to claim 21, wherein the rotorincludes one of nine and twelve fluid chambers.
 24. A hydraulictransformer according to claim 21, wherein the rotor gates are separatedby walls and the face plate gates and the rotor gates are dimensionedsuch that at least two rotor gates are of the same size, and the wallsbetween the rotor gates can close respective fluid chambers,simultaneously, for a particular position of the rotor.